Article pubs.acs.org/JAFC
Potential and Limitation of a New Defatted Diatom Microalgal Biomass in Replacing Soybean Meal and Corn in Diets for Broiler Chickens Richard E. Austic, Ahsan Mustafa, Byoungyun Jung, Stephanie Gatrell, and Xin Gen Lei* Department of Animal Science, Cornell University, Ithaca, New York 14853, United States S Supporting Information *
ABSTRACT: Three experiments were conducted to determine if defatted diatom Staurosira sp. biomass (DFA) (Cellana, Kailua-Kona, HI, USA) from biofuel production could replace a portion of soybean meal (SBM) and (or) corn in diets for broiler chicks. In experiment 1, 2-day-old chicks were fed diets with DFA at 0% (control), 7.5% replacing SBM, or 7.5 and 10% replacing SBM and corn. Chicks fed the DFA-containing diets had lower body weight gain (P < 0.05) than the controls in the starter period. Two follow-up experiments, experiments 2 and 3, indicated that supplementing the 7.5% DFA diet (replacing SBM) with amino acids, but not exogenous protease or electrolytes, restored growth performance of chicks to the control levels. Responses of plasma and liver biomarkers and gross examination of digestive tract showed no toxicity of DFA. In conclusion, DFA could substitute for 7.5% of SBM alone, or in combination with corn, in diets for broiler chicks when appropriate amino acids are added. KEYWORDS: defatted microalgal biomass, soybean meal, amino acids, growth, broiler chickens
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INTRODUCTION The global population is expected to reach 9 billion by the year 2050. Thus, the plant breeding community has been working toward doubling crop yields to keep up with future food demands.1 This might be very challenging as agricultural land is shrinking, global water tables are depleting,2 and crop inputs, especially chemical fertilizers, are reducing as a means of minimizing greenhouse gas emissions and the agricultural carbon footprint.3 Meanwhile, food-producing animals rely heavily on soybean meal (SBM) and corn to meet their protein and energy requirements, creating a direct competition of these two foods for human consumption. This competition will only exacerbate the future food demand as meat consumption in developing countries increases. Therefore, alternative protein and energy sources are required to replace SBM and corn in animal feeds for sustainable animal agriculture. Although single-cell protein sources such as microalgae are deemed suitable for animal or human consumption,4,5 their inclusion in animal feed has regained attention mainly due its role as a promising source for biofuel production.6 Diatoms comprise a large fraction of phytoplankton and are believed to be important contributors to the aquatic food web.7 The diatom microalga Staurosira sp. is currently under investigation as a potential source of oil for biofuel production. The defatted biomass (DFA) contains 19% crude protein, compared to 47.5 and 8.5% found in SBM and corn, respectively.8 Whereas the protein content of DFA makes it a suitable replacement of these two main ingredients in diets for swine and poultry, there is no report on such application or potential.9 Instead, there has been a good amount of research on specialized products that can be derived from these algae,10−12 because of their high contents of vitamins, minerals, antioxidants,5 long-chain polyunsaturated omega-3 fatty acids,13−16 and carotenoids.17−21 © 2013 American Chemical Society
Broiler chicks are the fastest growing and most efficient food species that is consumed worldwide. Whereas the domestic broiler industry produces 36 billion pounds of meat with U.S. $22 billon value,22 it also uses 13.5 and 30 million metric tons of SBM and corn per annum, respectively. Various algae have been tested as sources of protein for broiler chicks by replacing SBM or fish meal.17,18,23−27 Dietary levels from 5 to 10% algae substituted safely in partial replacement of these conventional ingredients.18,19,26 Similar results were seen in swine.28 However, higher levels of inclusion (20%) led to adverse effects on performance in poultry,25 probably due to relative deficiency in the sulfur-containing amino acids methionine and cysteine5 and (or) low digestibility of microalgal protein. Likely, increasing the amount or availability of certain amino acids may alleviate the negative effects seen at higher levels of algae inclusion. Protease may be added to enhance amino acid availability and to improve growth performance.29,30 Chemically, DFA are uniquely different from other microalgae. They are supposed to contain high levels of ash and silicon (Si) in their cell membranes and have unique morphological structures known as frustules.31 Like most algae, they exhibit considerably higher sodium contents than land-based plants.32 Because high levels of ash33 and sodium34 and the balance of monovalent minerals35,36 affect body metabolism and health status, it remains to be determined if the DFA inclusion into animal diets causes toxicity or side effects such as feed refusal. Therefore, the objective of the present study was to determine whether DFA of Staurosira sp. Received: Revised: Accepted: Published: 7341
May 4, 2013 June 21, 2013 July 4, 2013 July 4, 2013 dx.doi.org/10.1021/jf401957z | J. Agric. Food Chem. 2013, 61, 7341−7348
Journal of Agricultural and Food Chemistry
Article
could be used for partial replacement of SBM and (or) corn in diets of broiler chicks and if additional supplementation of amino acids, electrolytes, and protease improved its feeding values.
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Table 2. Typical Composition of Control and 7.5% AlgaeContaining Diets starter diets (0−3 weeks)
MATERIALS AND METHODS ingredient corn (yellow) soybean meal (48.5% CP) meat meal corn gluten meal corn oil dicalcium phosphate limestone salt vitamin mixa mineral mixb defatted diatom DL-methionine L-lysine hydrochloride L-isoleucine L-threonine L-tryptophan L-arginine (free base) total ingredients nutrient composition ME (kcal/g) protein, % fat, % fiber, % Ca, % P, % P, % (available)
Animals, Diets, and Management. The protocols of all experiments were approved by the Institutional Animal Care and Use Committee of Cornell University. Hatchling Ross broiler chicks were obtained from a commercial hatchery and housed in a temperature-controlled room at the Cornell University Poultry Research Farm. The broiler chicks were housed in thermostatically controlled cage batteries for 3 weeks and were transferred to grower cages at room temperature from 3 to 6 weeks. Chicks had free access to feed and water and were provided with a lighting schedule of 22 h light, 2 h dark daily. Body weights were recorded at the beginning of experiments and were recorded weekly thereafter, along with feed intake. The DFA of Staurosira sp. (Table 1) (Cellana, Kailua-Kona, HI,
Table 1. Chemical Composition of the Defatted Diatom Microalgal Biomass (DFA)a item
content
item
content
ME (kcal/g) protein fat ND fiberb AD fiberb ash moisture calcium (Ca) phosphorus (P) sodium (Na) potassium (K) magnesium (Mg) chloride (Cl) iron (Fe) copper (Cu) manganese (Mn) zinc (Zn) molybdenum (Mo) selenium (Se) taurine lanthionine
1.32 19.1 3.3 14.0 0.7 44.9 6.9 2.78 0.76 3.94 1.66 0.79 6.34 1820 4 101 25 2.2
